Comparing Multi-Modal Traffic Assignments in Large-Scale Simulations using the Macroscopic Fundamental Diagram: Mode Shift from Cars to Powered Two Wheelers

The Macroscopic Fundamental Diagram (MFD) relates traffic flow (vehicles/hour) and density (vehicles/km), and can be used to support decisions on how to mitigate traffic congestion in some region. The MFD is usually computed over an area characterized by a homogeneous traffic pattern. For this reason, when considering multiple traffic assignments for the same transportation infrastructure, the different patterns of traffic densities arising result in MFDs computed over different areas, which cannot be meaningfully compared. In order to allow the use of MFDs to compare the impact of different traffic assignments, partitioning of the region needs to be done based on an infrastructure metric that will not change the resulting area. This paper assesses the use of the administrative boundaries of a city to partition the area in a way that satisfies this requirement. Using this partitioning method, we show how MFDs can be used to quantify the impact of a mode shift from cars to powered two wheelers on traffic congestion in a city-scale multi-modal mobility simulation of Monaco. Our results show that it is possible to use administrative boundaries to generate MFDs, and to use them to evaluate the impact of multiple traffic assignments on the same transportation infrastructure.